Rapid antigen testing as a reactive public health response to surges in SARS-CoV-2 outbreak risk in healthcare settings

Smith, D. R.; Duval, A.; Zahar, J. R.; opatowski, l.; TEMIME, L.

Background: Surges in community SARS-CoV-2 incidence increase risk of importation and subsequent transmission in healthcare facilities. Antigen rapid diagnostic testing (Ag-RDT) is widely used for population screening, but its health and economic benefits as a reactive intervention in healthcare settings are unclear. Methods: We used stochastic, individual-based modelling to simulate SARS-CoV-2 transmission in a long-term care facility with varying COVID-19 containment measures in place (social distancing, face masks, vaccination). In contrast to routine symptomatic testing using reverse-transcriptase polymerase chain reaction (RT-PCR), we evaluated the efficacy and health-economic efficiency of single or repeated population-wide Ag-RDT screening interventions implemented in response to surges in nosocomial outbreak risk. Results: Depending on the baseline containment measures in place, nosocomial SARS-CoV-2 incidence was reduced by up to 40-47% (range of means) with routine RT-PCR testing, 59-63% with the addition of a timely round of Ag-RDT screening, and 69-75% with well-timed two-round screening. For the latter, a delay of 4 to 5 days between the first and second rounds was optimal for transmission prevention. Efficacy varied depending on test sensitivity, subpopulations targeted, and SARS-CoV-2 incidence in the community. Efficiency, however, varied primarily depending on the other containment measures in place: surveillance costs for a combined strategy of routine RT-PCR testing and reactive Ag-RDT screening ranged from a mean {euro}420-{euro}10,260/infection averted across scenarios (default unit costs: {euro}5/Ag-RDT test, {euro}50/RT-PCR test). Interpretation: Reactive Ag-RDT screening complements routine RT-PCR testing, and systematic two-round screening helps overcome limited, time-varying diagnostic sensitivity. Health-economic gains scale significantly with underlying nosocomial outbreak risk.